Slab deflection settings

Tekla Structural Designer
2021
Tekla Structural Designer

Slab deflection settings

The Slab Deflection page and its sub pages allow you to control the slab deflection defaults applied.

  • in the current project - when accessed by clicking Slab Deflection > Settings
  • in new projects - when accessed by clicking Home > Settings

New Load Event Defaults

Setting Description

Start time offset

Allows you to define a default start time offset value for new event load start times. The value of a new event load start time is always the previous event start time + the default start time offset.

Construction load

Allows you to define a default value for new construction loads.

Note:

The default construction load value depends on the head code that you are using.

New Check Defaults

Setting Description

Deflection limit, L /

When a new check is added to the Slab Deflection Check Catalogue it initially defaults to the deflection limit set here.

Aging, Creep & Shrinkage

Setting Description

Allowance for shrinkage effects in total deflection

Allows you to define an amplification base factor for shrinkage.

The value must be within the range from 0.1 to 0.9.

Aging Coefficient

Allows you to select between 2 creep/aging methods: User defined and Automatic.

Note:

The Aging Coefficient option is only available for the US head code.

Modification factors

Note: This sub-page is only displayed when the dialog box is accessed from the Slab Deflection ribbon.

Different factors can be applied for each of the different materials in the model in order to adjust the following properties:

E

Young's modulus

G

Shear modulus

Itorsion

Section inertia about local X

Imajor

Section inertia about local Y

Iminor

Section inertia about local Z

Area

Section area in compression or tension

Aparallel to minor

Section shear area in local Y

Aparallel to major

Section shear area in local Z

t

shell thickness (applicable to concrete only)

The factors also vary according to the member types, (and in the case of concrete members whether they are cracked or not). For concrete members in particular, design codes can require that analysis stiffness adjustment factors are applied since the appropriate properties to use in analysis are load and time dependent.

Note: Although default modification factors for each material are provided in the settings sets to reflect the design code being worked to, you should check that these are appropriate for your particular analysis model. If you make changes to any of the modification factors, analysis must be repeated.

Iterative Cracked Section Analysis

Setting Description
Note: This sub-page is only displayed when the dialog box is accessed from the Slab Deflection ribbon.

Global Convergence Criteria

Allows you to modify the following options:
  • Maximum number of iterations: The number of iterations to perform. Default = 200.
  • Tolerance: At the end of each iteration, values are checked against the previous iteration results. If the difference is less than the tolerance determined here, the result is converged, and the analysis is complete. Default = 0.00100.
  • Relative: Default: ON.
Tip:
To resolve global convergence failures:
  • Increase the value in Maximum number of iterations.
  • Decrease the value in Tolerance.

Local Convergence Criteria

Allows you to modify the following options:
  • Maximum number of iterations: The number of iterations to perform. Default = 500.
  • Tolerance: At the end of each iteration, values are checked against the previous iteration results. If the difference is less than the tolerance determined here, the result is converged, and the analysis is complete. Default = 0.000001.
  • Smoothing Parameter: A property only available for the Eurocode head code. Default = 0.005.
Tip:
To resolve local convergence failures:
  • Increase the value in Maximum number of iterations.
  • Decrease the value in Tolerance.
  • If you are using the Eurocode head code, increase the value in Smoothing Parameter.

Load Event Sequence

This sub-page is only displayed when accessed from Settings on the Home tab. It allows you to modify the global event sequence according to your needs.
Tip: The global event sequence provides the basis for the model event sequence that you can modify, whereas the model event sequence provides the basis for a submodel event sequence that you can modify.
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